1. Field of the Invention
The present invention relates to the recovery of tin from iron containing tin concentrates through the utilization of a suspension smelting reaction, and a high velocity gas reduction reaction carried out continuously.
2. Description of the Prior Art
Tin has been considered one of the more precious metals and has been recovered for 5000 years at relatively low temperatures from cassiterite ores in the presence of coal or carbon. In later times, however, it was necessary to use ore deposits which were less abundant in tin and more abundant in iron, making it necessary that the smelting be carried out in multistage processes, thereby substantially increasing the costs. At first, the smelting of such complex ores containing higher iron contents was considered economically not feasible, per se, so these ores were merely mixed with ores low in iron and rich in tin, and subsequently smelted.
With the development of wet metallurgy processes, new ways were found for the concentration of tin in the ore as well as for the separation of foreign metals. However, these methods although quite practical, have the disadvantage that they are relatively high in cost.
With the development of the volatilization method which today corresponds with the state of the art, it was possible to efficiently smelt complex, tin bearing ores. The process became economically of interest when it was found that the addition of pyrite, a tin sulfide, could be volatilized easily with relatively high steam pressures and this tin sulfide could be converted through combustion in the gas phase to tin oxide which after sublimation could be precipitated in the solid phase. One disadvantage, however, was the necessity of using a series of process steps which were expensive, used high amounts of energy, and provided some environmental problems.